Python script to transfer AJ-SR04M Waterproof Ultrasonic Sensor to MQTT

rainbarrel.py

# !/usr/bin/python
# encoding:utf-8

# Waterproof Ultrasonic Module AJ-SR04M

import RPi.GPIO as GPIO
import time
import paho.mqtt.client as mqtt

timeout = 1  # seconds wait for signal
TRIG = 27  # Associate pin 27 to TRIG
ECHO = 22  # Associate pin 22 to Echo

# MQTT setup
mqtt_broker = "YOUR_MQTT_SERVER"
mqtt_port = 1883
mqtt_topic_status = "devices/rainbarrel/status"
mqtt_topic_depth = "devices/rainbarrel/depth"

def on_publish(client, userdata, mid, reason_code, properties):
    # reason_code and properties will only be present in MQTTv5. It's always unset in MQTTv3
    try:
        userdata.remove(mid)
    except KeyError:
        print("Error on_publish")

mqttc = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2, protocol=mqtt.MQTTProtocolVersion.MQTTv5)
mqttc.on_publish = on_publish
unacked_publish = set()
mqttc.user_data_set(unacked_publish) # Set the user data variable passed to callbacks. May be any data type.

mqttc.connect(host=mqtt_broker, port=mqtt_port)
mqttc.loop_start()

# PIN setup
GPIO.setmode(GPIO.BCM)  # Set GPIO pin numbering
GPIO.setup(TRIG, GPIO.OUT)  # Set pin as GPIO out
GPIO.setup(ECHO, GPIO.IN)  # Set pin as GPIO in
GPIO.output(TRIG, False)  # Set TRIG as LOW

# settle
time.sleep(1)
print("Distance measurement in progress")

try:
    while True:
        GPIO.output(TRIG, True)  # Set TRIG as HIGH
        time.sleep(0.00001)  # Delay of 0.00001 seconds
        GPIO.output(TRIG, False)  # Set TRIG as LOW

        pulse_start = time.time()
        timeout_start = pulse_start
        while GPIO.input(ECHO) == 0:
            pulse_start = time.time()
            if pulse_start - timeout_start > timeout:
                break

        pulse_end = time.time()
        timeout_end = pulse_end
        if GPIO.input(ECHO) == 1:
            while GPIO.input(ECHO) == 1:
                pulse_end = time.time()
                if pulse_end - timeout_end > timeout:
                    break

        pulse_duration = pulse_end - pulse_start  # Pulse duration to a variable

        distance = pulse_duration * 17150  # Calculate distance
        distance = round(distance, 2)  # Round to two decimal points

        print("distance known, now processing")
        if 20 < distance < 400:  # Is distance within range
            msg_info = mqttc.publish(mqtt_topic_depth, distance, qos=1)
            unacked_publish.add(msg_info.mid)
            print("Distance:", distance, "cm")
        else:
            msg_info_status = mqttc.publish(mqtt_topic_status, f"Failed, pulse_start: {pulse_start}", qos=1)
            unacked_publish.add(msg_info_status.mid)
            print("Out Of Range: ", distance, "cm")
        while len(unacked_publish):
            time.sleep(0.1)
        time.sleep(10)

except KeyboardInterrupt:
    mqttc.disconnect()
    mqttc.loop_stop()
    print("Measurement stopped by User")
    GPIO.cleanup()

# chmod +x /home/pi/rainbarrel.py
# sudo chmod 644 /lib/systemd/system/rainbarrel.service

rainbarrel.service

[Unit]
Description=Rainbarrel sensor
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/python /home/pi/rainbarrel.py
Restart=on-abort
User=pi
WorkingDirectory=/home/pi

[Install]
WantedBy=multi-user.target